Learn how to program a spare key for your Mitsubishi Lancer Ralliart with a LAUNCH X431 scanner. Step-by-step guide, troubleshooting tips, and FAQs.

Quick Answer

Yes, you can add a spare key to a Mitsubishi Lancer Ralliart using a LAUNCH X431 scanner, provided you have the existing working key and the scan tool supports Mitsubishi immobilizer functions. The process involves reading the PIN code from the ECU, entering key programming mode, and registering the new transponder. Expect the procedure to take 10–20 minutes. A fully functional working key is required for this process, as the LAUNCH X431 cannot program a key if all keys are lost (that requires specialized dealer-level tools).

Why Adding a Spare Key to the Ralliart Isn’t a DIY Button Sequence

If you’ve owned older Mitsubishi models like the Galant or Lancer ES, you might remember programming a spare key by turning the ignition on and off in a specific pattern. The Ralliart is different. It uses the Mitsubishi FAST (Free-hand Advanced Security Transponder) system, which relies on a proximity-based key fob with a built-in transponder chip. The FAST system controls push-to-start operation and immobilizer functions through the ECU, not a simple remote receiver.

That means you cannot program a new key without a diagnostic tool that can talk to the immobilizer ECU. The LAUNCH X431 fills that gap by providing security access via the OBDII port. I’ve used this tool on several Ralliart and Evo X models, and the procedure is reliable as long as you follow each step carefully.

What You’ll Need Before You Start

Gather these items before connecting anything to your car:

LAUNCH X431 scanner – Any model with the Mitsubishi software package. Higher-end versions like the X431 V or X431 Pro include the immobilizer module by default, but entry-level models may require a separate purchase or subscription.
New, uncut Mitsubishi Ralliart key – It must be a blank FAST key specifically for the Ralliart system. Do not buy a standard key or a used key from another vehicle. The transponder in a used key is locked to its original VIN and cannot be reprogrammed by the LAUNCH X431.
Existing working key – This is mandatory. The scanner needs at least one recognized key to authenticate with the immobilizer ECU before it can add a new one.
Stable 12V battery – A weak battery is the #1 cause of programming failures. If your battery is even slightly low, connect a trickle charger. The programming process takes several minutes, and a voltage drop can corrupt the immobilizer memory.
VCI (Vehicle Communication Interface) – Either a wired OBDII cable or a Bluetooth adapter. I recommend using the USB cable if you run into repeated communication errors, as wireless connections can drop during the handshake.

Important: The LAUNCH X431 must have the latest Mitsubishi software installed. Log in to the LAUNCH Cloud before starting and check for updates. The immobilizer function sometimes appears under a separate “Security” add-on module – if you don’t see it in your menu, contact LAUNCH support to purchase access.

Step-by-Step: Adding a Spare Key with LAUNCH X431

I’ve broken this down into six stages. Take your time – rushing through a step can force you to start over or, worse, erase all keys from the ECU.

Step 1: Connect the LAUNCH X431 to the Vehicle

Turn the ignition OFF.
Plug the VCI into the OBDII port. On the Ralliart, you’ll find it under the driver’s side dashboard, just above the hood release lever.
Turn the ignition ON – just accessory power. Do not start the engine.
Power up the LAUNCH X431 tablet and open the diagnostic software.

The scanner should recognize the VCI automatically. If it says “Communication Error,” check the cable or Bluetooth pairing and try again.

Step 2: Select the Correct Vehicle Profile

From the main menu, tap Diagnostics.
Choose Mitsubishi from the manufacturer list.
Let the tool auto-detect the vehicle, or manually enter:
- Year: 2009–2015 (depending on your Ralliart)
- Model: Lancer (or Lancer Ralliart)
- Engine: 4B11T (2.0L Turbo)
- System: Immobilizer – this is critical. If you select “Engine” or “Body,” the immobilizer functions won’t appear.

Tip: If auto-detect fails, go to Mitsubishi > Lancer > (your year) > Immobilizer. The menu path varies slightly by software version, but “Immobilizer” is always listed separately from engine diagnostics.

Step 3: Read the PIN Code from the ECU

The immobilizer ECU requires a security code (PIN) before it lets you add keys. The LAUNCH X431 can read this PIN directly.

In the Immobilizer menu, select Read Immobilizer Data or Security Access (the wording depends on your software version).
The tool will query the ECU and display a 5-digit code.
Write this PIN down and keep it handy. Some procedures ask you to enter it manually later, and if the tool loses connection, you’ll need it to restart.

I’ve seen some users skip this step and then get stuck when the tool times out. Always record the PIN even if the screen says “No Action Required.”

Step 4: Enter Key Programming Mode

Return to the Immobilizer main menu.
Select Program Key or Add Key – choose “Add Key,” not “Replace All Keys,” unless you want to wipe all existing keys.
The scanner will prompt you to confirm that a working key is in the ignition. Keep the original key inserted.
The LAUNCH X431 communicates with the immobilizer ECU and requests authorization. This takes about 30 seconds.
A message appears: “Insert a key to be programmed” or “Ready to register new key.”

At this point, do not touch the push-start button or turn the ignition off. The scanner holds the session open, and any interruption forces you to restart from Step 1.

Step 5: Register the New Spare Key

Remove the original key from the ignition (or, if your Ralliart uses a push-button start with a slot, remove the key fob from the slot).
Immediately insert the new spare key into the ignition slot (or hold the new fob against the push-start button for FAST proximity models). The scanner expects the new key within a few seconds.
The LAUNCH X431 performs a handshake with the new transponder. You’ll see a progress bar or a “Waiting…” message.
After about 10–15 seconds, the screen should say “Key Registered Successfully.”
Remove the new key.

If the tool says “Key Not Recognized,” the new key is likely the wrong type (non-FAST) or a used key. Do not repeat the attempt with the same key – it will not work. Get a verified blank FAST key from a locksmith or dealer.

Step 6: Verify the New Key Works

Exit the diagnostic software.
Turn the ignition OFF and wait 10 seconds.
Test the new key:
- Lock and unlock the doors with the remote buttons.
- Press the push-start button – the dashboard should light up to ACCESSORY, then ON.
- Start the engine.
If the car starts and runs without the security light flashing, the programming worked.

If the engine stalls after starting or the security light stays on, the key was not fully registered. Repeat Steps 4–6, making sure you insert the new key promptly.

Troubleshooting Common Issues

Problem	Likely Cause	Solution
“Communication Error”	Weak battery, loose OBD connection	Charge battery, reconnect VCI, restart tool
“Security Access Denied”	Wrong PIN or VIN mismatch	Re-read PIN from ECU or contact LAUNCH support
“Key Not Recognized”	New key is incorrect type (non-FAST)	Verify key is specific to Ralliart FAST system
Tool stuck on “Waiting…” for more than 1 minute	Poor Bluetooth/WiFi connection	Use USB cable instead of wireless
All keys lost after programming	Accidental selection of “Replace All Keys”	You must contact a Mitsubishi dealer – LAUNCH cannot recover erased keys

If programming fails mid-process:

Do not turn off the ignition.
Re-connect the LAUNCH X431 and try Steps 1–5 again with the original key.
If the tool still fails, you may need to reprogram all keys (original included) using the “Replace All Keys” option – but only use that as a last resort.

Understanding the Ralliart Immobilizer System

The Lancer Ralliart uses a rolling code transponder system inside the FAST key fob. Each key contains a unique encrypted ID that the immobilizer ECU recognizes. The ECU can store up to four keys in its memory. When you add a key with the LAUNCH X431, the ECU simply appends the new ID to its list – it does not forget the existing keys.

Why the LAUNCH X431 works: This scan tool uses licensed Mitsubishi diagnostic protocols to authenticate with the immobilizer ECU. It bypasses the need for dealer-level security by reading the PIN directly from the ECU through the OBDII port. This is the same method used by many independent locksmiths.

What the LAUNCH X431 cannot do:

Recover a key from a damaged transponder (if the chip is physically broken, you need a new blank key)
Program a key if the ECU is dead or corrupted (requires replacement or dealer reflash)
Program keys on pre-2008 Mitsubishi models without additional adapter cables
Delete a single key individually (on some software versions, the only way to remove an old key is to use “Replace All Keys” – so plan ahead)

Frequently Asked Questions

Can I add a key without the original working key?

No. The LAUNCH X431 requires at least one working key to authenticate with the immobilizer ECU before it can program new keys. If all keys are lost, you must have a Mitsubishi dealer replace the immobilizer ECU or use a specialized dealer-level tool like the MUT-III. The LAUNCH X431 cannot help in that scenario.

Can I program a used key from another Mitsubishi?

Only if it is a blank, uncut key. A used key already contains a transponder locked to its original vehicle. The LAUNCH X431 cannot erase or reprogram a used key’s transponder – you need a new, blank key from a locksmith or dealer. Using a used key will result in a “Key Not Recognized” error.

How much does the LAUNCH X431 software cost for this procedure?

The LAUNCH X431 requires a Mitsubishi software package. Prices vary by model and subscription. Expect to pay around $50–$150 for a one-year license, or you can purchase a permanent module (often included with higher-end X431 models like the X431 V or X431 Pro). Check your tool’s included software before purchasing. If you only need one key programmed, paying a locksmith $80–$150 may be cheaper than buying the software.

Will this procedure work on the Mitsubishi Lancer Evolution (Evo X)?

Yes. The Evo X uses the same immobilizer and FAST system as the Ralliart. The LAUNCH X431 procedure is identical for both models. I’ve successfully coded keys on both platforms using the same steps.

How many spare keys can I add?

You can register up to four keys total (including the original). Once the ECU memory is full, you must delete old keys before adding new ones. The LAUNCH X431 offers a “Delete Key” function on some software versions – if you don’t see it, use “Replace All Keys” and then program all keys you want (including the original and up to three spares).

Why is my push-start button not working after programming?

If the engine starts with the physical key inserted but the push-start button doesn’t recognize the key fob, the FAST proximity sensor in the key may be defective, or the fob battery is dead. Replace the fob battery with a CR2032 coin cell and try again. The programming process only registers the transponder – remote lock/unlock and FAST proximity are separate systems that rely on the fob’s battery and RF module.

Can I program a key if my car has aftermarket modifications (alarm, remote start)?

Aftermarket systems often interfere with the immobilizer. I’ve seen aftermarket remote starters cause the LAUNCH X431 to lose communication mid-programming. You may need to temporarily disconnect or bypass the aftermarket system before using the scanner. If your car has a Viper or Compustar remote start, contact the installer for guidance. Some units require you to hold a sequence on the remote during programming.

What is the difference between “Add Key” and “Replace All Keys” on the LAUNCH X431?

Add Key: Preserves all existing keys and simply registers the new one. This is the safest option for adding a spare.
Replace All Keys: Erases EVERY key from the ECU’s memory, then programs only the key(s) you insert during that session. Use this only if you have lost all keys but still have one working (to start the process) or if you want to remove old keys from the system. Be extremely cautious – if you select “Replace All Keys” by mistake, you’ll need dealer help to recover.

My LAUNCH X431 does not have an “Immobilizer” option. What should I do?

Update your software via the LAUNCH Cloud. The immobilizer function is not available in the free/basic Mitsubishi package for some models. Contact LAUNCH support to purchase the “Security” or “Immobilizer” add-on module. Alternatively, some lower-end LAUNCH X431 models (like the X431 Diagun) may not support immobilizer functions at all – check your device specifications.

Can a locksmith do this cheaper than buying a LAUNCH X431?

If you only need one key programmed, a mobile locksmith with comparable equipment will charge $80–$150. That may be cheaper than purchasing the LAUNCH X431 software subscription. However, if you own multiple Mitsubishi vehicles or plan to program keys for friends and family, investing in the LAUNCH X431 pays for itself after two or three jobs. It also gives you the freedom to program keys anytime without waiting for a locksmith.

About the Author: Erwin Salarda is an Automotive Service Equipment Technician based in the Philippines, specializing in computerized automotive diagnostic equipment such as OBD scanners and wheel alignment systems. Since 2012, he has been actively providing technical support, equipment installation, troubleshooting, after-sales service, and hands-on training for automotive service equipment used by workshops and automotive professionals.

He has received specialized training from international suppliers and manufacturers, including Launch X431 in Shenzhen, China, Lawrence Engineering Company in Guangzhou, China, and 3Excel Wheel Alignment Company in Shenzhen, China. Through these trainings, he developed advanced expertise in automotive diagnostics, calibration, wheel alignment systems, and computerized automotive service technologies.

Erwin Salarda provides professional after-sales support and technical training for automotive diagnostic and wheel alignment equipment

Add Spare Key to Mitsubishi Lancer Ralliart Using LAUNCH X431